Despite numerous developments in lock technology, several problems still exist with conventional locks. Among the most familiar to vehicle manufacturers are problems related to pre-coded lock sets. Vehicles are typically provided with a set of locks, such as multiple door locks, a trunk lock, a glove box lock and/or an ignition lock. In most cases, two or more of the locks for a vehicle are operated with a common key. Where multiple locks for a vehicle are coded to the same key, the commonly-coded locks are often sent to a vehicle manufacturer together as a set. During vehicle assembly, these lock sets must be carefully labeled and tracked to ensure that they are installed in the same vehicle—even after being sent to different assembly stations or otherwise being moved to different locations in preparation for installation. When a vehicle is being assembled, it is important that each lock in the set be installed in the same vehicle. If locks from different sets get interchanged during assembly, multiple vehicles would have to have new locks installed. This can involve the removal of such vehicles from an assembly line and/or can cause the assembly line to be temporarily stopped. Thus, the use of pre-coded lock sets can be very costly and time consuming to vehicle manufactures.
Generally, a codeable lock is a lock that can be coded to a key after the lock has been assembled and/or after the lock has been installed. Typically, conventional codeable locks employ two-piece tumblers. These two-piece tumblers often have a first member that “reads” the coded surface of a key inserted in the lock assembly and a second member that can releasably engage a housing of the lock assembly. In such lock assemblies, the two tumbler members are normally not connected or otherwise engaged to one another prior to coding of the lock assembly. However, the code of the lock is determined at least in part upon the relationship between these two tumbler members when they are joined together. To join the member of each tumbler together in order to code the lock assembly, a key is inserted into the lock assembly. In some cases, the positions of the tumbler members change according to the depth of the key cut at the locations of the tumblers. Next, with the key still inserted, the two members of each tumbler are forced together to set the code for the tumblers. The relationship between the two pieces can be held by serrated edges on the pieces joined together. Thus, with a codeable lock, there is little to no concern regarding mixing lock sets together. Unfortunately, this type of codeable lock design has a number of inherent limitations that limit its feasibility for use in many applications (such as vehicular applications).
One problem with conventional codeable locks is that they normally do not enable enough coding sequences. Generally, a pre-coded lock has multiple tumblers that read the key surface in a number of positions along a key. For example, many pre-coded locks read the key surface at seven places along the key. At each of these positions, a key can have a number of different depths. In many locks for example, the key has five depths that are read by locks. Thus, many pre-coded locks are potentially capable of a large number of different codings (in some cases, over 70,000 combinations). Many codeable locks, however, cannot be coded to a large number of different depths of a key, or at least can only be coded to a fraction of the number of possible key depths. For example, rather than having five different depth codings per tumbler, some codeable locks are only capable of having a maximum of three depth codings per tumbler. A number of key and lock design considerations limit the number of practical codes for a key. For example, it is normally desirable to avoid key codes in which all or substantially all of the notch depths are the same. However, larger numbers of potential codes for a lock normally result in larger numbers of practical codes for the same lock.
One of the reasons why only a limited number of coding sequences is possible in conventional codeable locks is due to the serrated edges often employed in multiple-piece (e.g., two-piece) tumblers. In order for a conventional codeable lock to be strong enough to withstand attempts at picking or overpowering the lock, the serrations retaining the engagement of the tumbler members to one another must be relatively large. Since the size of a vehicle lock's barrel is already predetermined by a number of esthetic standards and other design considerations, these large serrations permit fewer coding variations between the members of each tumbler. One way a conventional codeable lock with a fixed barrel size could have more coding variations is to employ smaller serrations for the tumbler members. Unfortunately, this also makes the lock more susceptible to picking and overpowering and to inadvertent shifting between the two tumbler pieces.
Another significant limitation in conventional codeable locks is related to the linear movement of the two-piece tumblers sometimes employed. Specifically, conventional two-piece tumblers employ tumbler members that move in a linear fashion during the coding process. In other words, the key-engaging member is limited to linear displacement in response to contact with the key notch steps of the key surface. In a number of applications (including automotive applications), the maximum size of the key and the distance between the deepest and shallowest key notches are largely determined by esthetic considerations. An advantage of using two-piece pivotable tumblers in a codeable lock rather than using linearly-moving tumblers in a codeable lock is that the pivoting tumbler is capable of magnifying the key notch depths read by the tumbler. This is due to the fact that the length of an arc traced by a pivoting tumbler increases as the distance from the pivot point of the tumbler increases.
Another problem with conventional codeable locks is that such locks have normally been designed for use in building doors. The design constraints for vehicle door locks can be significantly greater than those for building door locks. For example, building door locks can often be made larger without consequence, thereby enabling such locks to have more room for more coding sequences. To scale the barrel down to the customary size of a barrel on a vehicle (where lock size and weight are typically much greater concerns) would only magnify the problems discussed above. In light of the problems and limitations of the prior art described above, a need exists for a codeable lock assembly that is reliable, can be relatively small, is strong enough to resist picking and overpowering, can be manufactured and assembled at relatively low cost, can have a large number of coded states, is simple to operate for purposes of coding the lock assembly, and can employ tumbler elements that pivot during the coding process. Each embodiment of the present invention achieves one or more of these results.